Fiber optic probe scatterometer for spectroscopy measurements

ABSTRACT

A device for making spectroscopy measurements with reduced or eliminated surface reflections is provided, the device including an elongated member including an outermost opaque thin walled enclosure; an optically transparent thin-walled enclosure adjacent an inner surface of said outermost thin walled enclosure; one or more optical fibers centrally and axially disposed and spaced apart a distance B with respect to the optically transparent thin-walled enclosure; wherein the elongated member is adapted to be coupled to a spectrometer and an illumination source to provide a light signal from the illumination source along said optically transparent thin-walled enclosure and collect a scattered light signal from the sample by said one or more optical fibers to provide to the spectrometer.

TECHNICAL FIELD

This disclosure generally relates to spectroscopy measurement methodsand apparatus including at infrared (IR) wavelengths, and moreparticularly Fiber Optic Probes for making Non-Destructive spectroscopymeasurements including evaluation of the condition of organic containingmaterials, including fiber reinforced composite materials, such asaircraft structural composite materials.

BACKGROUND

IR spectroscopy measurements may be useful for a variety of purposesincluding aerospace, automotive and industrial applications, as well asbiological and bio-medical applications. For example, infrared (IR)radiation is readily absorbed by organic materials in association withrelative motions (vibrations) of atoms such as carbon, hydrogen, oxygenand nitrogen. As such, IR spectroscopy measurements may indicate acondition of a wide variety or organic materials.

For example, organic polymer materials such as resin-fiber composites oradhesives may change over time due to a variety of reasons includingheat exposure. Chemical changes to a polymer containing structure mayaffect the desired properties of the polymer containing structureincluding structural integrity such as strength of a composite or theadhesive properties of an adhesive.

One problem with prior art approaches to making IR Spectroscopymeasurements of polymer containing materials is that a signal-to-noiseratio may be insufficient to determine relative changes in chemistry ofthe material. For example, prior art Fiber Optic Probes have failed toaddress the problem of Fresnel reflections from a surface of a samplewhich may obscure molecular absorption and/or fluorescence spectral datathat may be present in the scattered light signal from within a sample.

In addition, prior art devices and methods for making IR Spectroscopymeasurements of polymer containing materials have the drawback that theymay only be able to measure the outer surface of the material. Forexample, prior art IR Spectroscopy approaches typically requiredestruction of a material in an ex-situ setting.

Accordingly, there is a need for an improved spectroscopynon-destructive testing device and method for using the same tonon-destructively determine a condition of organic containing materials,including fiber reinforced composite materials, over small samplingareas and/or in hard-to-access configurations with a suitablesignal-to-noise ratio.

SUMMARY

In one embodiment, a device for making spectroscopy measurements withreduced or eliminated surface reflections is provided, the deviceincluding an elongated member including an outermost opaque thin walledenclosure; an optically transparent thin-walled enclosure adjacent aninner surface of said outermost thin walled enclosure; one or moreoptical fibers centrally and axially disposed and spaced apart adistance B with respect to the optically transparent thin-walledenclosure; wherein the elongated member is adapted to be coupled to aspectrometer and an illumination source to provide a light signal fromthe illumination source along said optically transparent thin-walledenclosure and collect a scattered light signal from the sample by saidone or more optical fibers to provide to the spectrometer.

In another embodiment, A method of non-destructively determining thecondition of an organic containing material sample with reduced oreliminated surface reflections is provided, the method includingproviding an elongated member including an outermost opaque thin walledenclosure; providing an optically transparent thin-walled enclosureadjacent an inner surface of said outermost thin walled enclosure;providing one or more optical fibers centrally and axially disposed andspaced apart a distance B with respect to the optically transparentthin-walled enclosure; positioning said distal end of said opticallytransparent thin-walled enclosure adjacent said organic containingmaterial sample; providing an interrogating light signal from anillumination source to said sample along said optically transparentthin-walled enclosure; and collecting a scattered light signal from saidsample by said one or more optical fibers and providing said scatteredlight signal to a spectrometer.

These and other objects, aspects and features of the disclosure will bebetter understood from a detailed description of the preferredembodiments of the disclosure which are further described below inconjunction with the accompanying Figures.

BRIEF DESCRIPTION OF THE ILLUSTRATIONS

FIG. 1 is a side view of a portion of a fiber optic probe scatterometerassembly in a spectroscopy measurement configuration according to anembodiment.

FIG. 2 is a cross sectional view of the measuring end of the fiber opticprobe scatterometer according to an embodiment.

FIG. 3 is a process flow diagram including several embodiments of thedisclosure including using the IR fiber optic needle probe.

FIG. 4 is a flow diagram of an aircraft and service methodologyaccording to an embodiment.

FIG. 5 is a block diagram of an aircraft according to an embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present disclosure achieves the foregoing objects, aspects andfeatures by providing a fiber optic probe scatterometer for accessingsmall sampling areas and/or hard-to-access or normally inaccessibleareas and surfaces for performing non-destructive spectroscopymeasurements.

It will be appreciated that the fiber optic probe scatterometer of thepresent disclosure may be suitably used to non-destructively evaluateany material using any suitable interrogating wavelength of light, butis particularly advantageous for non-destructively evaluating byinfrared (IR) spectroscopy, organic containing materials, includingfiber reinforced composite materials. The fiber optic probescatterometer is particularly useful in obtaining spectral data wherethe sample size desired is on the order of the diameter or width of thefiber optic probe scatterometer, or where the desired sampling surfaceis accessible through a small opening.

It will further be appreciated that although the fiber optic probescatterometer of the present disclosure is explained with exemplary usewith respect to a carbon fiber-resin composite material, such as alayered carbon composite structure, that the fiber optic probescatterometer and method of using the same may be equally applicable tothe measurement of any organic material having a small sample sizeand/or accessible through only a small opening, including applicationsin aerospace, automotive, and industrial fields, as well as biological,medical, and biomedical fields.

Referring to FIG. 1 is shown a side view of the fiber optic probescatterometer assembly according to an embodiment of the disclosure. Afiber optic probe scatterometer 10 may be coupled to one or more fiberoptic cables e.g., 11A, 11B, which may in turn be respectively coupledto a spectrometer, e.g., 12A, and an illumination source 12B. Thespectrometer 12A may be any spectrometer that may be interfaced withfiber optics, including a hand-held spectrometer. It will be appreciatedthat the illumination source 12B and the spectrometer 12A may be housedtogether in a single instrument and that the signal interrogating e.g.,11B and signal collection cable, e.g., 11A may be housed as a singlecable including coaxial signal carrying capability.

In one embodiment, the spectrometer 12A may have the ability to makeinfrared (IR) spectroscopic reflectance measurements including amulti-frequency broadband infrared detection capability includingnear-IR, midwave-IR, and far-IR wavelengths and the illumination source12B may have the ability to provide a broadband of interrogating IRwavelengths including near-IR, midwave-IR, and far-IR wavelengths. Inone embodiment, the illumination source 12B and the spectrometer 12A mayhave an ability to make IR spectroscopy measurements over the wavelengthregion of about 500 to about 4000 nanometers.

In some embodiments, the spectrometer used to make the measurement mayuse measurement techniques such as reflectance including specular and/ordiffuse reflectance. The illumination source 12B may include amulti-frequency infrared source and the spectrometer 12A may include aninfrared detector that includes multi-frequency infrared detectioncapability.

In one embodiment, the diameter of a measuring end (distal end) 10A ofthe fiber optic probe scatterometer 10, may have a diameter that enablesthe measuring end 10A to fit through a slightly larger sized hole e.g.,15 within a polymer containing material, such as a fiber (e.g., carbon)reinforced composite structure e.g., 14 in order to access an interiorportion such as an interior layer e.g., 14A.

For example, in some embodiments, the fiber optic probe scatterometermeasuring end 10A may have a diameter (shown below in FIG. 2 as C) ofless than about 2 mm, more preferably less than about 1.5 mm, and evenmore preferably about 1 mm in diameter or less. It will be appreciatedthat the ‘small opening’ through which the measuring end may be insertedmay be larger than the measuring end diameter and that the sampled sizemay be smaller than the measuring end diameter.

Referring to FIG. 2, is shown an enlarged view of a portion of themeasuring end 10A of the fiber optic probe scatterometer 10. In someembodiments, the measuring end 10A of the IR fiber optic probescatterometer may be of different lengths, depending on the application,e.g., the distance required to access a normally inaccessible organicmaterial containing surface (e.g., the surface of interior layer 14A ofcomposite material 14). For example, in some embodiments, the length ofthe measuring end of the fiber optic probe scatterometer 10A may be fromabout 1 to about 10 inches in length.

The fiber optic probe scatterometer 10 may include one or more signalreceiving optical fibers 16 located axially and centrally (coaxially)with respect to a first outer thin walled tube 18 (jacket) and a secondinner concentric thin walled tube 20 (illumination tube). In oneembodiment, a single signal receiving optical fiber 16 is providedaxially and centrally (coaxially) with respect to the outer tubes 18 and20 to collect a scattered light signal.

In some embodiments the one or more axially and centrally locatedoptical fibers 16 have a diameter of about 100 microns to about 500microns, more preferably from about 100 microns to about 300 microns,more preferably from about 150 microns to about 250 microns. As shown,the one or more optical fibers 16 collects a scattered light opticalsignal from the interior of the probed sample e.g., 14A over a signalcollection volume, e.g., 16B while reducing or eliminating collection ofsample surface reflections. The one or more optical fibers may be formedof an IR transparent material such as fused silica, preferably low-OHfused silica (dehydroxylated fused silica). Optical fibers whichtransmit further into the IR, such as silicon fibers and chalcogenideglass fibers, are known in the art. The one or more optical fibers maybe coated with a low refractive index cladding as is known in the art.

In one embodiment, an interrogating optical signal from the illuminationsource e.g., 12B is provided through the second inner concentric thinwalled tube 20 (illumination tube). For example, the illumination tube20 is preferably transparent to the wavelength of interrogatingillumination used and may be coated with a low refractive index claddingas is known in the art that allows propagation of light through theillumination tube by total internal reflection. In one embodiment, theillumination tube 20 may be formed of an IR transparent material such asfused silica, preferably low-OH fused silica (dehydroxylated fusedsilica). In one embodiment the illumination tube 20 may have a wallthickness of from about 10 microns to about 500 microns.

The jacket (outermost) tube 18 may be any structurally stiff and opaquematerial, and in one embodiment, may be a metal tube, and in anotherembodiment may be a steel tube, such as a stainless steel tube.Preferably, the illumination tube 20 fits snugly and concentricallywithin the jacket tube 18. In one embodiment the jacket tube 18 may havea wall thickness of from about thickness of about 10 microns to about500 microns.

In another embodiment, a structural filler material, e.g., 22 may beincluded to fill the gap between the one or more optical fibers 16 andthe illumination tube 20. The filler material may be an opaque material,such as one or more of a powder metal oxide, glass, or polymer material.

In one embodiment, the one or more optical fibers 16 have a tip (distalend) 16A that is terminated within (axially set back from) a planedefined by the distal ends 18A of the outermost tube 18 which may beco-planar with a sample in contact with the distal ends 18A of theoutermost tube 18. In some embodiments, the tip 16A may be axially setback from the distal end of the outermost tube 18A by a distance A, ofabout 100 to about 500 microns, more preferably from about 200 to about300 microns, even more preferably about 250 microns. In otherembodiments, the tip 16A may be axially set back from the distal end ofthe outermost tube 18A by between about 1 and about 2 diameters of theone or more optical fibers 16. In another embodiment, the distal ende.g., 20A of the illumination tube 20 and the tip 16A may be axially setback from the distal end of the outermost tube 18A by about the samedistance A.

Thus, in one embodiment, the distance A may be selected in order toimprove a signal-to-noise ratio by reducing or eliminating surfacereflected (Fresnel reflections e.g., specular or diffuse) light fromentering the one or more signal collection optical fibers 16. Forexample, the amount of surface reflected light that undesirablycontributes to the signal may be reduced or eliminated by decreasing thesetback distance A, e.g., from the tip of one or more optical fibers 16Ato a plane that is co-planar with a sample surface. In addition, thesetback distance A allows the tip 16A of the one or more optical fibersto be protected from contact with the sample while allowing the distalend 18A of the outermost tube 18 to contact the sample.

In another embodiment, additionally or alternatively to selecting thedistance A, a gap distance B, e.g., radial distance B between the innerdiameter of the illumination tube 20 and a total outer diameter of theone or more signal collection optical fibers 16 may be selected toimprove a signal-to-noise ratio by reducing or eliminating surfacereflected light from entering the one or more optical fibers 16. By theterm ‘total outer diameter’ of the one or more optical fibers is meant aminimum outer diameter necessary to enclose the one or more opticalfibers. For example, the amount of surface reflected light thatundesirably contributes to the signal may be reduced or eliminated byincreasing a radial gap distance B.

In operation, the illumination tube may provide a cone of illuminatione.g., 24A into the sample e.g., 14A, and the scattered light opticalsignal from within the sample e.g., 24B may be collected by the one ormore signal collection optical fibers 16 which receive the scatteredlight signal within a conical field of regard e.g., 16B. Thus, bycontrolling one or more of the distances A and B, as well as the size ofthe signal collection volume within the sample 16B, the signal to noiseratio may be improved to a level sufficient to allow molecular(chemical) changes within a sample to be more accurately determined. Inone embodiment, the size of the signal collection volume 16B may becontrolled by selecting the radial gap distance B and the setbackdistance A such that a width or diameter of the conical field of regard16B of the signal collection fiber or fibers 16 will intersect with theillumination cone of light projected from the end of the illuminationtube 20 only within the interior of the sample, in a definable andcontrollable manner. Thus, the signal collection field of regard 16B ofthe signal collection optical fibers 16 may not encompass scattered orreflected light from the upper surface of the sample lying directlyunder the illumination tube, thereby reducing or eliminating collectionof surface reflected light by the one or more optical fibers 16.

It will be appreciated that the distal ends of the outermost tube 18A ofthe optical scatterometer probe may be placed in contact with a surfaceof a sample, e.g., 14A to be measured which may serve to providestability and a repeatable and known distance between the signalcollection optical fiber end e.g., 16A and the sample surface, therebyallowing comparison of collected spectra to comparable spectra collectedon a sample of a known chemical and/or physical condition (relativecalibration spectra).

Referring again to FIG. 1, in exemplary operation, the measuring end 10Aof the fiber optic probe scatterometer 10 is inserted into a smallopening 15 (e.g., about 1 mm or less) in an external surface of a fiber(e.g., carbon) reinforced composite panel 14 (which may be a structuralportion of an aircraft e.g., fuselage or wing), where the hole 15 may beslightly larger than the measuring end 10A of the fiber optic probescatterometer 10. The tip of the fiber optic probe scatterometer 10,such as the distal ends of the jacket tube 18A, may be in contact orproximate to a surface, to be measured, such as an inner layer of fiberreinforced composite panel 14A. In some embodiments, it will beappreciated that the measurement may be non-destructive and may be madein-situ, e.g., in the field without removing the structural component.It will be appreciated that industry (aircraft) specific requirementsmay limit the size of the hole or opening that may be permissible in astructural component to not more than (0.040 inches) (e.g., not morethan about 1.0 mm).

Referring again to FIG. 2, in operation, an interrogating light signalof a selected band of wavelengths e.g., 24A is provided to the samplesurface by the illumination tube, a portion of which propagates into theinterior the sample, where it is absorbed and reemitted e.g., 24B intothe field of view (within signal collection volume 16B) of a signalcollection fiber e.g., 16. As will be appreciated, by reducing oreliminating collection of light reflected from the surface of thesample, the signal strength of re-emitted absorbed light from within thevolume of the sample may be improved, thereby allowing more accurate anddetailed interrogation of molecular changes occurring within the sample.The absorbed and re-emitted light e.g., 24B is then collected by the oneor more signal collection optical fibers e.g., 16 and transferred to thespectrometer 12A for spectral analysis.

In one embodiment, the spectrometer 12A may include appropriate softwaree.g., 12C either in memory or in storage media accessible by amicroprocessor included in or separate from the spectrometer 12A, forcomparing the spectral signal of the illumination source and changesimparted by absorption of light by the sample. The software may furtherinclude spectral storage capabilities (able to access memory or storagemedia accessible by a microprocessor included in or separate from thespectrometer 12A) to track relative spectral changes in a sample overtime.

In another embodiment, spectroscopic measurements may be made bydetermining relative differences and/or similarities in measured spectrawith respect to spectra from a relative calibration of control samples,such as samples that have been exposed to a known amount and/or type ofenvironmental stress and whose material and/or chemical properties areknown, e.g., determined by separate physical property and/or chemicaltesting.

It will be appreciated that an Absorbance at one or more wavelengths maybe calculated according to well known equations based on the intensityof reflected IR light measured, e.g., a diffuse reflectance measurement.It will also be appreciated that depending on the wavelength of theregion interrogated, that the absorbance peaks represent complex motionsof organic materials including the relative motions (vibrations) ofatoms such as carbon, hydrogen, oxygen and nitrogen. Thus, depending onthe chemical and/or material property changes associated with spectralchanges in a material, a determination as to whether the changesrepresent acceptable or unacceptable chemical and/or material propertychanges may be made e.g., by associating a particular absorbance (orreflectance) at one or more wavelengths with a particular acceptableand/or unacceptable absorbance (or reflectance) threshold.

For example, evaluation of the IR spectroscopy measurement may be madein-situ (in the field) automatically by a controller included in orconnected to a hand-held or portable IR spectrometer according to apreprogrammed series of steps including providing an indication (e.g.,alarm or signal) indicating unacceptable IR spectroscopy measurementvalues above or below a predetermined threshold. Alternatively, or inaddition, the IR spectroscopy measurement results may be stored inmemory included in or connected to the IR spectrometer for lateranalysis.

Referring to FIG. 3 is shown a process flow diagram including severalembodiments of the present disclosure. In step 301, an opening suitablefor inserting the fiber optic probe scatterometer 10 may be provided ina first surface in order to access a normally inaccessible organicmaterial containing second surface interior with respect to the firstsurface. In process 303, a measuring end of the fiber optic probescatterometer may be inserted through the opening and positionedproximate the organic material containing surface. In process 305, thefiber optic probe scatterometer may be coupled to an IR spectrometer andone or more wavelengths of IR light provided through the fiber opticprobe scatterometer to the organic material containing surface through aprobe illumination tube. In step 307 reflected IR light (spectra) (e.g.,with minimal or no surface reflected light) may be collected by one ormore optical fibers central and coaxial with respect to the illuminationtube and provided to the IR spectrometer. In step 309, a condition ofthe organic material may be determined based on relative changes in thespectra compared to reference spectra including a known condition of thematerial.

Referring next to FIGS. 4 and 5, embodiments of the disclosure may beused in the context of an aircraft manufacturing and service method 78as shown in FIG. 4 and an aircraft 94 as shown in FIG. 5. Duringpre-production, exemplary method 78 may include specification and design80 of the aircraft 94 and material procurement 82. During production,component and subassembly manufacturing 84 and system integration 86 ofthe aircraft 94 takes place. Thereafter, the aircraft 94 may go throughcertification and delivery 88 in order to be placed in service 90. Whilein service by a customer, the aircraft 94 may be scheduled for routinemaintenance and service 92 (which may also include modification,reconfiguration, refurbishment, and so on).

Each of the processes of method 78 may be performed or carried out by asystem integrator, a third party, and/or an operator (e.g., a customer).For the purposes of this description, a system integrator may includewithout limitation any number of aircraft manufacturers and major-systemsubcontractors; a third party may include without limitation any numberof vendors, subcontractors, and suppliers; and an operator may be anairline, leasing company, military entity, service organization, and soon.

As shown in FIG. 5, the aircraft 94 produced by exemplary method 78 mayinclude an airframe 98 with a plurality of systems 96 and an interior100. Examples of high-level systems 96 include one or more of apropulsion system 102, an electrical system 104, a hydraulic system 106,and an environmental system 108. Any number of other systems may beincluded. Although an aerospace example is shown, the principles of theembodiments may be applied to other industries, such as the automotiveindustry.

The apparatus embodied herein may be employed during any one or more ofthe stages of the production and service method 78. For example,components or subassemblies corresponding to production process 84 maybe fabricated or manufactured in a manner similar to components orsubassemblies produced while the aircraft 94 is in service. Also, one ormore apparatus embodiments may be utilized during the production stages84 and 86, for example, by substantially expediting assembly of orreducing the cost of an aircraft 94. Similarly, one or more apparatusembodiments may be utilized while the aircraft 94 is in service, forexample and without limitation, to maintenance and service 92.

While the embodiments illustrated in the Figures and described above arepresently preferred, it should be understood that these embodiments areoffered by way of example only. The disclosure is not limited to aparticular embodiment, but extends to various modifications,combinations, and permutations as will occur to the ordinarily skilledartisan that nevertheless fall within the scope of the appended claims.

1. A device for making spectroscopy measurements with reduced oreliminated surface reflections comprising: an elongated membercomprising an outermost opaque thin walled enclosure; an opticallytransparent thin-walled enclosure adjacent an inner surface of saidoutermost thin walled enclosure; one or more optical fibers centrallyand axially disposed and spaced apart a distance B with respect to theoptically transparent thin-walled enclosure; wherein said elongatedmember is adapted to be coupled to a spectrometer and an illuminationsource to provide a light signal from said illumination source alongsaid optically transparent thin-walled enclosure and collect a scatteredlight signal from said sample by said one or more optical fibers toprovide to said spectrometer.
 2. The device of claim 1, wherein saidoutermost thin walled enclosure comprises a distal end that that extendsa first distance past said distal end of said optically transparentthin-walled enclosure and a second distance A past a distal end of saidone or more optical fibers, said second distance A reducing oreliminating signal collection by said one or more optical fibers ofsurface reflections from said sample.
 3. The device of claim 2 whereinsaid first distance is equal to said second distance A.
 4. The device ofclaim 2 wherein said one or more optical fibers has a total width ofbetween about 150 and 250 microns and said distance A is between about200 and 300 microns.
 5. The device of claim 1, further comprising anopaque material disposed between the optically transparent thin-walledenclosure and the one or more optical fibers.
 6. The device of claim 1,wherein the outermost opaque thin walled enclosure width comprises awidth of less than about 1.5 mm.
 7. The device of claim 1 wherein saiddistance B is such that a light signal collection field of viewprojected adjacent said distal end of said one or more optical fibersand into an adjacent sample minimizes or eliminates signal collection bysaid one or more optical fibers of reflected light from a surface ofsaid sample.
 8. The device of claim 1 wherein said distance B is aboutequal to or greater than a total width of said one or more opticalfibers.
 9. The device of claim 1 wherein the outermost opaque thinwalled enclosure comprises a tube.
 10. The device of claim 1 wherein theoutermost opaque thin walled enclosure comprises a metal.
 11. The deviceof claim 1 wherein the outermost opaque thin walled enclosure comprisessteel.
 12. The device of claim 1 wherein the one or more optical fibersconsists of a single optical fiber.
 13. The device of claim 12 whereinthe single optical fiber has a diameter of from about 150 microns toabout 250 microns.
 14. The device of claim 1, wherein said elongatedmember is coupled to said spectrometer and said illumination source. 15.The device of claim 14, wherein said spectrometer and said illuminationsource comprise an infrared (IR) spectrometer and IR illuminationsource.
 16. A method of non-destructively determining the condition ofan organic containing material sample with reduced or eliminated surfacereflections comprising: providing an elongated member comprising anoutermost opaque thin walled enclosure; providing an opticallytransparent thin-walled enclosure adjacent an inner surface of saidoutermost thin walled enclosure; providing one or more optical fiberscentrally and axially disposed and spaced apart a distance B withrespect to the optically transparent thin-walled enclosure; positioningsaid distal end of said optically transparent thin-walled enclosureadjacent said organic containing material sample; providing aninterrogating light signal from an illumination source to said samplealong said optically transparent thin-walled enclosure; and collecting ascattered light signal from said sample by said one or more opticalfibers and providing said light signal to a spectrometer.
 17. The methodof claim 16, wherein said distal end of said optically transparentthin-walled enclosure is placed in contact with said sample.
 18. Themethod of claim 16, wherein said elongated probe is placed through aninspection opening adjacent said sample.
 19. The method of claim 18,wherein said inspection opening is less than about 1.5 mm.
 20. Themethod of claim 16, further comprising the step of comparing spectracomprising said scattered light signal to reference spectra to determinerelative spectral changes in said sample.
 21. The method of claim 20,wherein said reference spectra is associated with a reference samplewith known physical and/or chemical properties.
 22. The method of claim20, further comprising the step of determining whether the organiccontaining material sample is in an acceptable condition based on saidcomparison.
 23. The method of claim 22, wherein said organic containingmaterial comprises a fiber reinforced composite material.
 24. The methodof claim 22, wherein said organic containing material comprises a carbonfiber reinforced composite material.
 25. The method of claim 22, whereinsaid organic containing material comprises an aircraft structuralcomponent.
 26. The method of claim 16, wherein said spectrometer andsaid illumination source comprise an infrared (IR) spectrometer and IRillumination source.
 27. The method of claim 16, wherein said outermostthin walled enclosure comprises a distal end that that extends a firstdistance past said distal end of said optically transparent thin-walledenclosure and a second distance A past a distal end of said one or moreoptical fibers, said distance A selected to reduce or eliminate signalcollection by said one or more optical fibers of surface reflectionsfrom said sample.
 28. The method of claim 24 wherein said first distanceis equal to said second distance A.
 29. The method of claim 24 whereinsaid one or more optical fibers has a total width of between about 150and 250 microns and said distance A is between about 200 and 300microns.
 30. The method of claim 16, further comprising providing anopaque material disposed between the optically transparent thin-walledenclosure and the one or more optical fibers.
 31. The method of claim16, wherein the outermost opaque thin walled enclosure width comprises awidth of less than about 1.5 mm.
 32. The method of claim 16, whereinsaid distance B is such that a light signal collection field of viewprojected adjacent said distal end of said one or more optical fibersand into an adjacent sample minimizes or eliminates signal collection bysaid one or more optical fibers of reflected light from a surface ofsaid sample.
 33. The method of claim 16 wherein said distance B is aboutequal to or greater than a total width of said one or more opticalfibers.
 34. The method of claim 16 wherein the outermost opaque thinwalled enclosure comprises a tube.
 35. The method of claim 16 whereinthe outermost opaque thin walled enclosure comprises a metal.
 36. Themethod of claim 16 wherein the outermost opaque thin walled enclosurecomprises steel.
 37. The method of claim 16 wherein the one or moreoptical fibers consists of a single optical fiber.
 38. The method ofclaim 37 wherein the single optical fiber has a diameter of from about150 microns to about 250 microns.